Medicine traditionally utilizes pharmacologic agents or surgical interventions for the treatment of disease. Specific targeting or localization of pharmacologic or biological agents to desired organs and tissues is a complex challenge. For example, cancer is a leading cause of death for both men and women in the United States (Jemal et al., CA Cancer J. Clin., 56:106-130, 2006). Current methods of cancer treatment include chemotherapy, radiation treatment, and surgical resection. As evidenced by high rates of cancer recurrence and low survival, treatments of conditions such as cancer often remain relatively ineffective.
Other diseases and conditions which utilize drug delivery technologies include immunological applications, pain control, wound healing, infectious disease, transplants, and the development of vaccines. Potential drug candidates often present solubility, toxicity, and pharmacokinetic considerations. Thus, there is a widespread need for targeted and sustained delivery of therapeutic agents.
Certain polyesters, polycarbonates, and polyamides are biodegradable polymers with low toxicity and degradation properties. Such polymers include poly(ε-caprolactone), poly(p-dioxanone), poly(trimethylene carbonate), poly(amino acids), and most notably poly(glycolic acid) and poly(lactic acid)(see, e.g., Agrawal et al., Biomaterials, 13:176-182, 1992; Attawia et al., J. Biomed. Mater. Res., 29:1233-140, 1995; Heller et al., Adv. Drug Deliv. Rev., 54:1015-1039, 2002; Miller and Williams, Biomaterials, 8:129-137, 1987; and Athanasiou et al., Arthroscopy, 14:726-737, 1998). These polymers are used in a variety of applications including the delivery of therapeutic agents. However, physical properties of the aforementioned polymers are often limited by monomer selection, polymerization techniques, and post-polymerization modifications. Properties of interest include thermal transition temperatures, bulk strength, flexibility, elasticity, degradation, crystallinity, and hydrophobicity. When polymers are utilized for in vivo applications, the physical properties of the material affect host response. Hence, a need exists for polymers and delivery systems with desired characteristics that are effective for treatment of diseases and conditions.